Phanatical, perhaps the nature of the subject could also be influential. If we take the stereotype that girls are better at humanities and boys are better at the maths and sciences, then that could provide a reason for the differences in marks in legal studies (admittedly, this stereotype doesn’t always exists)
You’ve used legal studies as an example but have you considered the performance between genders in a maths or science subject? It would be interesting to see whether girls still outperformed guys in that area at your school. Isolating the case of legal studies is a bit restricting as it doesn’t look at the overall trend.
Alternatively, it could just be your school where you see the trend of guys having a disadvantage.
Also, you speak about equality in society and that the feminist movement seeks to:
“encourage the achievement of women’s rights and downplay those of men”
(apologise I rarely post so I don’t know how to properly quote in a text box what you said). I suggest that the reason why women’s rights are recognised is because for a long time those rights weren’t didn’t exist for women. Correct me if I’m wrong but wasn’t it just last century (1900s) that women were given the right the vote in Australia? For men, rights accorded to them have been taken for granted as they have always been present to them. I don’t consider that men’s rights are being downplayed. Instead, it’s recognition that women are being given the same right/s as men, and as a result, is recognising the achievement towards a more equal society where women are given the same equality to men.
With the percentage of men at uni, again, you’ve confined the argument to a particular sample, that of University of Sydney students. Whilst ratio of males to females at Usyd may favour females, have you considered that it’s due to the course offerings at Usyd? To my understanding, USYd is the place to go for Law, Arts & Social Sciences. I’ve heard UNSW is the place to go for Commerce and Engineering related studies. So perhaps the uneven proportion of male students at your uni can be explained by University specialiations. You'd need to look at a wider sample of universities to see whether the lower ration of males to females is present.
Another explanation may be the fact that there are more vocational courses which guys choose to undertake and which don’t require a degree e.g. Electricians, mechanics, plumbers. Perhaps those alternative career paths are more appealing for guys than going to university and may offer an explanation for the lower male ratio.
The above are a few things for you to consider. Sorry for the long posting!